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Du J, Kong Y, Wen Y, Shen E, Xing H. HUH Endonuclease: A Sequence-specific Fusion Protein Tag for Precise DNA-Protein Conjugation. Bioorg Chem 2024; 144:107118. [PMID: 38330720 DOI: 10.1016/j.bioorg.2024.107118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Revised: 01/01/2024] [Accepted: 01/09/2024] [Indexed: 02/10/2024]
Abstract
Synthetic DNA-protein conjugates have found widespread applications in diagnostics and therapeutics, prompting a growing interest in developing chemical biology methodologies for the precise and site-specific preparation of covalent DNA-protein conjugates. In this review article, we concentrate on techniques to achieve precise control over the structural and site-specific aspects of DNA-protein conjugates. We summarize conventional methods involving unnatural amino acids and self-labeling proteins, accompanied by a discussion of their potential limitations. Our primary focus is on introducing HUH endonuclease as a novel generation of fusion protein tags for DNA-protein conjugate preparation. The detailed conjugation mechanisms and structures of representative endonucleases are surveyed, showcasing their advantages as fusion protein tag in sequence selectivity, biological orthogonality, and no requirement for DNA modification. Additionally, we present the burgeoning applications of HUH-tag-based DNA-protein conjugates in protein assembly, biosensing, and gene editing. Furthermore, we delve into the future research directions of the HUH-tag, highlighting its significant potential for applications in the biomedical and DNA nanotechnology fields.
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Affiliation(s)
- Jiajun Du
- Institute of Chemical Biology and Nanomedicine, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, School of Chemistry and Chemical Engineering Hunan University Changsha, Hunan 410082, PR China
| | - Yuhan Kong
- Institute of Chemical Biology and Nanomedicine, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, School of Chemistry and Chemical Engineering Hunan University Changsha, Hunan 410082, PR China
| | - Yujian Wen
- Institute of Chemical Biology and Nanomedicine, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, School of Chemistry and Chemical Engineering Hunan University Changsha, Hunan 410082, PR China
| | - Enxi Shen
- Institute of Chemical Biology and Nanomedicine, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, School of Chemistry and Chemical Engineering Hunan University Changsha, Hunan 410082, PR China
| | - Hang Xing
- Institute of Chemical Biology and Nanomedicine, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, School of Chemistry and Chemical Engineering Hunan University Changsha, Hunan 410082, PR China.
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2
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Off-Target Integron Activity Leads to Rapid Plasmid Compensatory Evolution in Response to Antibiotic Selection Pressure. mBio 2023; 14:e0253722. [PMID: 36840554 PMCID: PMC10127599 DOI: 10.1128/mbio.02537-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023] Open
Abstract
Integrons are mobile genetic elements that have played an important role in the dissemination of antibiotic resistance. Under stress, the integron can generate combinatorial variation in resistance cassette expression by cassette reshuffling, accelerating the evolution of resistance. However, the flexibility of the integron integrase site recognition motif hints at potential off-target effects of the integrase on the rest of the genome that may have important evolutionary consequences. Here, we test this hypothesis by selecting for increased-piperacillin-resistance populations of Pseudomonas aeruginosa with a mobile integron containing a difficult-to-mobilize β-lactamase cassette to minimize the potential for adaptive cassette reshuffling. We found that integron activity can decrease the overall survival rate but also improve the fitness of the surviving populations. Off-target inversions mediated by the integron accelerated plasmid adaptation by disrupting costly conjugative genes otherwise mutated in control populations lacking a functional integrase. Plasmids containing integron-mediated inversions were associated with lower plasmid costs and higher stability than plasmids carrying mutations albeit at the cost of a reduced conjugative ability. These findings highlight the potential for integrons to create structural variation that can drive bacterial evolution, and they provide an interesting example showing how antibiotic pressure can drive the loss of conjugative genes. IMPORTANCE Tackling the public health challenge created by antibiotic resistance requires understanding the mechanisms driving its evolution. Mobile integrons are widespread genetic platforms heavily involved in the spread of antibiotic resistance. Through the action of the integrase enzyme, integrons allow bacteria to capture, excise, and shuffle antibiotic resistance gene cassettes. This integrase enzyme is characterized by its ability to recognize a wide range of recombination sites, which allows it to easily capture diverse resistance cassettes but which may also lead to off-target reactions with the rest of the genome. Using experimental evolution, we tested the off-target impact of integron activity. We found that integrons increased the fitness of the surviving bacteria through extensive genomic rearrangements of the plasmids carrying the integrons, reducing their ability to spread horizontally. These results show that integrons not only accelerate resistance evolution but also can generate extensive structural variation, driving bacterial evolution beyond antibiotic resistance.
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3
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Wu R, Lv L, Wang C, Gao G, Yu K, Cai Z, Liu Y, Yang J, Liu JH. IS 26-Mediated Formation of a Hybrid Plasmid Carrying mcr-1.1. Infect Drug Resist 2022; 15:7227-7234. [PMID: 36533252 PMCID: PMC9748602 DOI: 10.2147/idr.s390765] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 11/23/2022] [Indexed: 09/29/2023] Open
Abstract
PURPOSE The objective of this study was to elucidate the characteristics and mechanism of formation of the fusion plasmid pHNSHP24 carrying mcr-1.1. MATERIALS AND METHODS mcr-1.1-bearing Escherichia coli SHP24 and the corresponding transconjugant were subjected to whole-genome sequencing (WGS) combining the Illumina and MinION platforms to obtain the complete sequences of the fusion plasmid and its original plasmids. RESULTS Complete sequence analysis and S1 nuclease-pulsed field gel electrophoresis (S1-PFGE) results indicated that E. coli SHP24 carried four plasmids: mcr-1.1-harboring phage-like plasmid pHNSHP24-3, F53:A-:B- plasmid pHNSHP24-4, pHNSHP24-1, and pHNSHP24-2. However, the plasmid pHNSHP24 carrying mcr-1.1 presents in the transconjugant differed from the four plasmids in the donor strain SHP24. Further analysis showed that pHNSHP24 may be the fusion product of pHNSHP24-3 and pHNSHP24-4 and is formed through a replicative transposition mechanism mediated by IS26 in E. coli SHP24. CONCLUSION This study is the first to report the fusion of an mcr-1.1-harboring phage-like pO111 plasmid and an F53:A-:B- plasmid mediated by IS26. Our findings revealed the role of phage-like and fusion plasmids in the dissemination of mcr-1.1.
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Affiliation(s)
- Renjie Wu
- Key Laboratory of Zoonosis of Ministry of Agricultural and Rural Affairs, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animal, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
| | - Luchao Lv
- Key Laboratory of Zoonosis of Ministry of Agricultural and Rural Affairs, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animal, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
| | - Chengzhen Wang
- Key Laboratory of Zoonosis of Ministry of Agricultural and Rural Affairs, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animal, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
| | - Guolong Gao
- Key Laboratory of Zoonosis of Ministry of Agricultural and Rural Affairs, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animal, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
| | - Kaiyang Yu
- Key Laboratory of Zoonosis of Ministry of Agricultural and Rural Affairs, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animal, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
| | - Zhongpeng Cai
- Key Laboratory of Zoonosis of Ministry of Agricultural and Rural Affairs, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animal, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
| | - Yiyun Liu
- Key Laboratory of Zoonosis of Ministry of Agricultural and Rural Affairs, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animal, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
| | - Jun Yang
- Key Laboratory of Zoonosis of Ministry of Agricultural and Rural Affairs, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animal, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
| | - Jian-Hua Liu
- Key Laboratory of Zoonosis of Ministry of Agricultural and Rural Affairs, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animal, College of Veterinary Medicine, South China Agricultural University, Guangzhou, People’s Republic of China
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, People’s Republic of China
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Laroussi H, Aoudache Y, Robert E, Libante V, Thiriet L, Mias-Lucquin D, Douzi B, Roussel Y, Chauvot de Beauchêne I, Soler N, Leblond-Bourget N. Exploration of DNA processing features unravels novel properties of ICE conjugation in Gram-positive bacteria. Nucleic Acids Res 2022; 50:8127-8142. [PMID: 35849337 PMCID: PMC9371924 DOI: 10.1093/nar/gkac607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 06/02/2022] [Accepted: 07/02/2022] [Indexed: 11/30/2022] Open
Abstract
Integrative and conjugative elements (ICEs) are important drivers of horizontal gene transfer in prokaryotes. They are responsible for antimicrobial resistance spread, a major current health concern. ICEs are initially processed by relaxases that recognize the binding site of oriT sequence and nick at a conserved nic site. The ICESt3/Tn916/ICEBs1 superfamily, which is widespread among Firmicutes, encodes uncanonical relaxases belonging to a recently identified family called MOBT. This family is related to the rolling circle replication initiators of the Rep_trans family. The nic site of these MOBT relaxases is conserved but their DNA binding site is still unknown. Here, we identified the bind site of RelSt3, the MOBT relaxase from ICESt3. Unexpectedly, we found this bind site distantly located from the nic site. We revealed that the binding of the RelSt3 N-terminal HTH domain is required for efficient nicking activity. We also deciphered the role of RelSt3 in the initial and final stages of DNA processing during conjugation. Especially, we demonstrated a strand transfer activity, and the formation of covalent DNA-relaxase intermediate for a MOBT relaxase.
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Affiliation(s)
- Haifa Laroussi
- Université de Lorraine, INRAE, DynAMic, F-54000, Nancy, France
| | - Yanis Aoudache
- Université de Lorraine, INRAE, DynAMic, F-54000, Nancy, France
| | - Emilie Robert
- Université de Lorraine, INRAE, DynAMic, F-54000, Nancy, France
| | | | - Louise Thiriet
- Université de Lorraine, INRAE, DynAMic, F-54000, Nancy, France
| | | | | | - Yvonne Roussel
- Université de Lorraine, INRAE, DynAMic, F-54000, Nancy, France
| | | | - Nicolas Soler
- Université de Lorraine, INRAE, DynAMic, F-54000, Nancy, France
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Heilers JH, Reiners J, Heller EM, Golzer A, Smits SHJ, van der Does C. DNA processing by the MOBH family relaxase TraI encoded within the gonococcal genetic island. Nucleic Acids Res 2019; 47:8136-8153. [PMID: 31276596 PMCID: PMC6736028 DOI: 10.1093/nar/gkz577] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 06/18/2019] [Accepted: 06/26/2019] [Indexed: 11/26/2022] Open
Abstract
Relaxases of the MOBH family are often found on large plasmids, genetic islands and integrative conjugative elements. Many members of this family contain an N-terminal relaxase domain (TraI_2) followed by a disordered middle part and a C-terminal domain of unknown function (TraI_2_C). The TraI_2 domain contains two putative metal-binding motifs, an HD domain motif and an alternative 3H motif. TraI, encoded within the gonococcal genetic island of Neisseria gonorrhoeae, is the prototype of the MOBH family. SAXS experiments showed that TraI_2 and TraI_2_C form globular structures separated by an extended middle domain. The TraI_2 domain cleaves oriT-ssDNA in a site-specific Mn2+ or Co2+ dependent manner. The minimal oriT encompasses 50 nucleotides, requires an inverted repeat 3′ of the nic-site and several nucleotides around nic for efficient cleavage. Surprisingly, no stable covalent relaxase-DNA intermediate was observed. Mutagenesis of conserved tyrosines showed that cleavage was abolished in the Y212A mutant, whereas the Y212F and Y212H mutants retained residual activity. The HD and the alternative 3H motifs were essential for cleavage and the HD domain residues D162 and D267 for metal ion binding. We propose that the active site binds two metal ions, one in a high-affinity and one in a low-affinity site.
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Affiliation(s)
- Jan-Hendrik Heilers
- Institute for Biology II, Microbiology, Albert Ludwig University Freiburg, 79104 Freiburg, Germany
| | - Jens Reiners
- Biochemie I, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany.,Center for Structural Studies, Heinrich Heine University, 40225 Düsseldorf, Germany
| | | | - Annika Golzer
- Institute for Biology II, Microbiology, Albert Ludwig University Freiburg, 79104 Freiburg, Germany
| | - Sander H J Smits
- Biochemie I, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany.,Center for Structural Studies, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Chris van der Does
- Institute for Biology II, Microbiology, Albert Ludwig University Freiburg, 79104 Freiburg, Germany
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6
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Agúndez L, Zárate-Pérez F, Meier AF, Bardelli M, Llosa M, Escalante CR, Linden RM, Henckaerts E. Exchange of functional domains between a bacterial conjugative relaxase and the integrase of the human adeno-associated virus. PLoS One 2018; 13:e0200841. [PMID: 30016371 PMCID: PMC6049929 DOI: 10.1371/journal.pone.0200841] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 07/02/2018] [Indexed: 12/21/2022] Open
Abstract
Endonucleases of the HUH family are specialized in processing single-stranded DNA in a variety of evolutionarily highly conserved biological processes related to mobile genetic elements. They share a structurally defined catalytic domain for site-specific nicking and strand-transfer reactions, which is often linked to the activities of additional functional domains, contributing to their overall versatility. To assess if these HUH domains could be interchanged, we created a chimeric protein from two distantly related HUH endonucleases, containing the N-terminal HUH domain of the bacterial conjugative relaxase TrwC and the C-terminal DNA helicase domain of the human adeno-associated virus (AAV) replicase and site-specific integrase. The purified chimeric protein retained oligomerization properties and DNA helicase activities similar to Rep68, while its DNA binding specificity and cleaving-joining activity at oriT was similar to TrwC. Interestingly, the chimeric protein could catalyse site-specific integration in bacteria with an efficiency comparable to that of TrwC, while the HUH domain of TrwC alone was unable to catalyze this reaction, implying that the Rep68 C-terminal helicase domain is complementing the TrwC HUH domain to achieve site-specific integration into TrwC targets in bacteria. Our results illustrate how HUH domains could have acquired through evolution other domains in order to attain new roles, contributing to the functional flexibility observed in this protein superfamily.
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Affiliation(s)
- Leticia Agúndez
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
| | - Francisco Zárate-Pérez
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, United States of America
| | - Anita F. Meier
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
| | - Martino Bardelli
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
| | - Matxalen Llosa
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC-SODERCAN, Santander, Spain
- * E-mail: (EH); (ML)
| | - Carlos R. Escalante
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, United States of America
| | - R. Michael Linden
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
| | - Els Henckaerts
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
- * E-mail: (EH); (ML)
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Zrimec J, Lapanje A. DNA structure at the plasmid origin-of-transfer indicates its potential transfer range. Sci Rep 2018; 8:1820. [PMID: 29379098 PMCID: PMC5789077 DOI: 10.1038/s41598-018-20157-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 01/10/2018] [Indexed: 11/29/2022] Open
Abstract
Horizontal gene transfer via plasmid conjugation enables antimicrobial resistance (AMR) to spread among bacteria and is a major health concern. The range of potential transfer hosts of a particular conjugative plasmid is characterised by its mobility (MOB) group, which is currently determined based on the amino acid sequence of the plasmid-encoded relaxase. To facilitate prediction of plasmid MOB groups, we have developed a bioinformatic procedure based on analysis of the origin-of-transfer (oriT), a merely 230 bp long non-coding plasmid DNA region that is the enzymatic substrate for the relaxase. By computationally interpreting conformational and physicochemical properties of the oriT region, which facilitate relaxase-oriT recognition and initiation of nicking, MOB groups can be resolved with over 99% accuracy. We have shown that oriT structural properties are highly conserved and can be used to discriminate among MOB groups more efficiently than the oriT nucleotide sequence. The procedure for prediction of MOB groups and potential transfer range of plasmids was implemented using published data and is available at http://dnatools.eu/MOB/plasmid.html.
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Affiliation(s)
- Jan Zrimec
- Institute of Metagenomics and Microbial Technologies, 1000, Ljubljana, Slovenia. .,Faculty of Health Sciences, University of Primorska, 6320, Izola, Slovenia. .,Department of Biology and Biological Engineering, Chalmers University of Technology, 412 96, Göteborg, Sweden.
| | - Aleš Lapanje
- Institute of Metagenomics and Microbial Technologies, 1000, Ljubljana, Slovenia. .,Department of Nanotechnology, Saratov State University, 410012, Saratov, Russian Federation. .,Department of Environmental Sciences, Institute Jožef Štefan, 1000, Ljubljana, Slovenia.
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Abstract
All plasmids that spread by conjugative transfer encode a relaxase. That includes plasmids that encode the type IV secretion machinery necessary to mediate cell to cell transfer, as well as mobilizable plasmids that exploit the existence of other plasmids' type IV secretion machinery to enable their own lateral spread. Relaxases perform key functions in plasmid transfer by first binding to their cognate plasmid as part of a multiprotein complex called the relaxosome, which is then specifically recognized by a receptor protein at the opening of the secretion channel. Relaxases catalyze a site- and DNA-strand-specific cleavage reaction on the plasmid then pilot the single strand of plasmid DNA through the membrane-spanning type IV secretion channel as a nucleoprotein complex. In the recipient cell, relaxases help terminate the transfer process efficiently and stabilize the incoming plasmid DNA. Here, we review the well-studied MOBF family of relaxases to describe the biochemistry of these versatile enzymes and integrate current knowledge into a mechanistic model of plasmid transfer in Gram-negative bacteria.
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Kishida K, Inoue K, Ohtsubo Y, Nagata Y, Tsuda M. Host Range of the Conjugative Transfer System of IncP-9 Naphthalene-Catabolic Plasmid NAH7 and Characterization of Its oriT Region and Relaxase. Appl Environ Microbiol 2017; 83:e02359-16. [PMID: 27742684 PMCID: PMC5165122 DOI: 10.1128/aem.02359-16] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 10/06/2016] [Indexed: 12/21/2022] Open
Abstract
NAH7 and pWW0 from gammaproteobacterial Pseudomonas putida strains are IncP-9 conjugative plasmids that carry the genes for degradation of naphthalene and toluene, respectively. Although such genes on these plasmids are well-characterized, experimental investigation of their conjugation systems remains at a primitive level. To clarify these conjugation systems, in this study, we investigated the NAH7-encoded conjugation system by (i) analyzing the origin of its conjugative transfer (oriT)-containing region and its relaxase, which specifically nicks within the oriT region for initiation of transfer, and (ii) comparing the conjugation systems between NAH7 and pWW0. The NAH7 oriT (oriTN) region was located within a 430-bp fragment, and the strand-specific nicking (nic) site and its upstream sequences that were important for efficient conjugation in the oriTN region were identified. Unlike many other relaxases, the NAH7 relaxase exhibited unique features in its ability to catalyze, in a conjugation-independent manner, the site-specific intramolecular recombination between two copies of the oriTN region, between two copies of the pWW0 oriT (oriTW) region (which is clearly different from the oriTN region), and between the oriTN and oriTW regions. The pWW0 relaxase, which is also clearly different from the NAH7 relaxase, was strongly suggested to have the ability to conjugatively and efficiently mobilize the oriTN-containing plasmid. Such a plasmid was, in the presence of the NAH7Δnic derivative, conjugatively transferable to alphaproteobacterial and betaproteobacterial strains in which the NAH7 replication machinery is nonfunctional, indicating that the NAH7 conjugation system has a broader host range than its replication system. IMPORTANCE Various studies have strongly suggested an important contribution of conjugative transfer of catabolic plasmids to the rapid and wide dissemination of the plasmid-loaded degradation genes to microbial populations. Degradation genes on such plasmids are often loaded on transposons, which can be inserted into the genomes of the recipient bacterial strains where the transferred plasmids cannot replicate. The aim was to advance detailed molecular knowledge of the determinants of host range for plasmids. This aim is expected to be easily and comprehensively achieved using an experimental strategy in which the oriT region is connected with a plasmid that has a broad host range of replication. Using such a strategy in this study, we showed that (i) the NAH7 oriT-relaxase system has unique properties that are significantly different from other well-studied systems and (ii) the host range of the NAH7 conjugation system is broader than previously thought.
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Affiliation(s)
- Kouhei Kishida
- Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Kei Inoue
- Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Yoshiyuki Ohtsubo
- Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Yuji Nagata
- Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Masataka Tsuda
- Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
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10
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Godziszewska J, Moncalián G, Cabezas M, Bartosik AA, de la Cruz F, Jagura-Burdzy G. Concerted action of NIC relaxase and auxiliary protein MobC in RA3 plasmid conjugation. Mol Microbiol 2016; 101:439-56. [PMID: 27101775 DOI: 10.1111/mmi.13401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/19/2016] [Indexed: 11/29/2022]
Abstract
Conjugative transfer of the broad-host-range RA3 plasmid, the archetype of the IncU group, relies on the relaxase NIC that belongs to the as yet uncharacterized MOBP4 subfamily. NIC contains the signature motifs of HUH relaxases involved in Tyr nucleophilic attack. However, it differs in the residue involved in His activation for cation coordination and was shown here to have altered divalent cation requirements. NIC is encoded in the mobC-nic operon preceded directly by oriT, where mobC encodes an auxiliary transfer protein with a dual function: autorepressor and stimulator of conjugative transfer. Here an interplay between MobC and NIC was demonstrated. MobC is required for efficient NIC cleavage of oriT in supercoiled DNA whereas NIC assists MobC in repression of the mobC-nic operon. A 7-bp arm of IR3 (IR3a) was identified as the binding site for NIC and the crucial nucleotides in IR3a for NIC recognition were defined. Fully active oriTRA3 was delineated to a 47-bp DNA segment encompassing a conserved cleavage site sequence, the NIC binding site IR3a and the MobC binding site OM . This highly efficient RA3 conjugative system with defined requirements for minimal oriT could find ample applications in biotechnology and computational biology where simple conjugative systems are needed.
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Affiliation(s)
- Jolanta Godziszewska
- Institute of Biochemistry and Biophysics PAS, Department of Microbial Biochemistry, 02-106 Warsaw, Poland.,Warsaw University of Life Sciences (WULS-SGGW), Faculty of Human Nutrition and Consumer Sciences, Laboratory of Food Chemistry, 02-776, Warsaw, Poland
| | - Gabriel Moncalián
- Departamento de Biología Molecular and Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC, C/Albert Einstein 22, 39011, Santander, Spain
| | - Matilde Cabezas
- Departamento de Biología Molecular and Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC, C/Albert Einstein 22, 39011, Santander, Spain
| | - Aneta A Bartosik
- Institute of Biochemistry and Biophysics PAS, Department of Microbial Biochemistry, 02-106 Warsaw, Poland
| | - Fernando de la Cruz
- Departamento de Biología Molecular and Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC, C/Albert Einstein 22, 39011, Santander, Spain
| | - Grazyna Jagura-Burdzy
- Institute of Biochemistry and Biophysics PAS, Department of Microbial Biochemistry, 02-106 Warsaw, Poland
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Fernández-González E, Bakioui S, Gomes MC, O'Callaghan D, Vergunst AC, Sangari FJ, Llosa M. A Functional oriT in the Ptw Plasmid of Burkholderia cenocepacia Can Be Recognized by the R388 Relaxase TrwC. Front Mol Biosci 2016; 3:16. [PMID: 27200362 PMCID: PMC4853378 DOI: 10.3389/fmolb.2016.00016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 04/14/2016] [Indexed: 12/14/2022] Open
Abstract
Burkholderia cenocepacia is both a plant pathogen and the cause of serious opportunistic infections, particularly in cystic fibrosis patients. B. cenocepacia K56-2 harbors a native plasmid named Ptw for its involvement in the Plant Tissue Watersoaking phenotype. Ptw has also been reported to be important for survival in human cells. Interestingly, the presence of PtwC, a homolog of the conjugative relaxase TrwC of plasmid R388, suggests a possible function for Ptw in conjugative DNA transfer. The ptw region includes Type IV Secretion System genes related to those of the F plasmid. However, genes in the adjacent region shared stronger homology with the R388 genes involved in conjugative DNA metabolism. This region included the putative relaxase ptwC, a putative coupling protein and accessory nicking protein, and a DNA segment with high number of inverted repeats and elevated AT content, suggesting a possible oriT. Although we were unable to detect conjugative transfer of the Ptw resident plasmid, we detected conjugal mobilization of a co-resident plasmid containing the ptw region homologous to R388, demonstrating the cloned ptw region contains an oriT. A similar plasmid lacking ptwC could not be mobilized, suggesting that the putative relaxase PtwC must act in cis on its oriT. Remarkably, we also detected mobilization of a plasmid containing the Ptw oriT by the R388 relaxase TrwC, yet we could not detect PtwC-mediated mobilization of an R388 oriT-containing plasmid. Our data unambiguously show that the Ptw plasmid harbors DNA transfer functions, and suggests the Ptw plasmid may play a dual role in horizontal DNA transfer and eukaryotic infection.
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Affiliation(s)
- Esther Fernández-González
- Departamento de Biología Molecular, Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria, UC-SODERCAN-Consejo Superior de Investigaciones Científicas Santander, Spain
| | - Sawsane Bakioui
- Institut National de la Santé et de la Recherche Médicale, U1047Nimes, France; UFR de Médecine Site de Nimes, U1047, Université de MontpellierFrance
| | - Margarida C Gomes
- Institut National de la Santé et de la Recherche Médicale, U1047Nimes, France; UFR de Médecine Site de Nimes, U1047, Université de MontpellierFrance
| | - David O'Callaghan
- Institut National de la Santé et de la Recherche Médicale, U1047Nimes, France; UFR de Médecine Site de Nimes, U1047, Université de MontpellierFrance
| | - Annette C Vergunst
- Institut National de la Santé et de la Recherche Médicale, U1047Nimes, France; UFR de Médecine Site de Nimes, U1047, Université de MontpellierFrance
| | - Félix J Sangari
- Departamento de Biología Molecular, Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria, UC-SODERCAN-Consejo Superior de Investigaciones Científicas Santander, Spain
| | - Matxalen Llosa
- Departamento de Biología Molecular, Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria, UC-SODERCAN-Consejo Superior de Investigaciones Científicas Santander, Spain
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12
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Sagredo S, de la Cruz F, Moncalián G. Design of Novel Relaxase Substrates Based on Rolling Circle Replicases for Bioconjugation to DNA Nanostructures. PLoS One 2016; 11:e0152666. [PMID: 27027740 PMCID: PMC4814116 DOI: 10.1371/journal.pone.0152666] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 03/17/2016] [Indexed: 11/28/2022] Open
Abstract
During bacterial conjugation and rolling circle replication, HUH endonucleases, respectively known as relaxases and replicases, form a covalent bond with ssDNA when they cleave their target sequence (nic site). Both protein families show structural similarity but limited amino acid identity. Moreover, the organization of the inverted repeat (IR) and the loop that shape the nic site differs in both proteins. Arguably, replicases cleave their target site more efficiently, while relaxases exert more biochemical control over the process. Here we show that engineering a relaxase target by mimicking the replicase target, results in enhanced formation of protein-DNA covalent complexes. Three widely different relaxases, which belong to MOBF, MOBQ and MOBP families, can properly cleave DNA sequences with permuted target sequences. Collaterally, the secondary structure that the permuted targets acquired within a supercoiled plasmid DNA resulted in poor conjugation frequencies underlying the importance of relaxase accessory proteins in conjugative DNA processing. Our results reveal that relaxase and replicase targets can be interchangeable in vitro. The new Rep substrates provide new bioconjugation tools for the design of sophisticated DNA-protein nanostructures.
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Affiliation(s)
- Sandra Sagredo
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Consejo Superior de Investigaciones Científicas-SODERCAN, C/ Albert Einstein 22, 39011, Santander, Spain
| | - Fernando de la Cruz
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Consejo Superior de Investigaciones Científicas-SODERCAN, C/ Albert Einstein 22, 39011, Santander, Spain
- * E-mail: (FC); (GM)
| | - Gabriel Moncalián
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Consejo Superior de Investigaciones Científicas-SODERCAN, C/ Albert Einstein 22, 39011, Santander, Spain
- * E-mail: (FC); (GM)
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13
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Sagredo S, Pirzer T, Aghebat Rafat A, Goetzfried MA, Moncalian G, Simmel FC, de la Cruz F. Orthogonale Assemblierung von Proteinen auf DNA-Nanostrukturen mithilfe von Relaxasen. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201510313] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Sandra Sagredo
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria; Universidad de Cantabria-Consejo Superior de Investigaciones Científicas-SODERCAN; Albert Einstein 22 39011 Santander Spanien
| | - Tobias Pirzer
- Physik-Department E14 und ZNN/WSI; TU München; Am Coulombwall 4a 85748 Garching Deutschland
| | - Ali Aghebat Rafat
- Physik-Department E14 und ZNN/WSI; TU München; Am Coulombwall 4a 85748 Garching Deutschland
| | - Marisa A. Goetzfried
- Physik-Department E14 und ZNN/WSI; TU München; Am Coulombwall 4a 85748 Garching Deutschland
| | - Gabriel Moncalian
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria; Universidad de Cantabria-Consejo Superior de Investigaciones Científicas-SODERCAN; Albert Einstein 22 39011 Santander Spanien
| | - Friedrich C. Simmel
- Physik-Department E14 und ZNN/WSI; TU München; Am Coulombwall 4a 85748 Garching Deutschland
| | - Fernando de la Cruz
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria; Universidad de Cantabria-Consejo Superior de Investigaciones Científicas-SODERCAN; Albert Einstein 22 39011 Santander Spanien
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14
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Sagredo S, Pirzer T, Aghebat Rafat A, Goetzfried MA, Moncalian G, Simmel FC, de la Cruz F. Orthogonal Protein Assembly on DNA Nanostructures Using Relaxases. Angew Chem Int Ed Engl 2016; 55:4348-52. [PMID: 26915475 PMCID: PMC5067690 DOI: 10.1002/anie.201510313] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 12/17/2015] [Indexed: 12/19/2022]
Abstract
DNA-binding proteins are promising reagents for the sequence-specific modification of DNA-based nanostructures. Here, we investigate the utility of a series of relaxase proteins-TrwC, TraI, and MobA-for nanofunctionalization. Relaxases are involved in the conjugative transfer of plasmids between bacteria, and bind to their DNA target sites via a covalent phosphotyrosine linkage. We study the binding of the relaxases to two standard DNA origami structures-rodlike six-helix bundles and flat rectangular origami sheets. We find highly orthogonal binding of the proteins with binding yields of 40-50 % per binding site, which is comparable to other functionalization methods. The yields differ for the two origami structures and also depend on the position of the binding sites. Due to their specificity for a single-stranded DNA target, their orthogonality, and their binding properties, relaxases are a uniquely useful addition to the toolbox available for the modification of DNA nanostructures with proteins.
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Affiliation(s)
- Sandra Sagredo
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Consejo Superior de Investigaciones Científicas-SODERCAN, Albert Einstein 22, 39011, Santander, Spain
| | - Tobias Pirzer
- Physik-Department E14 and ZNN/WSI, TU Munich, Am Coulombwall 4a, 85748, Garching, Germany
| | - Ali Aghebat Rafat
- Physik-Department E14 and ZNN/WSI, TU Munich, Am Coulombwall 4a, 85748, Garching, Germany
| | - Marisa A Goetzfried
- Physik-Department E14 and ZNN/WSI, TU Munich, Am Coulombwall 4a, 85748, Garching, Germany
| | - Gabriel Moncalian
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Consejo Superior de Investigaciones Científicas-SODERCAN, Albert Einstein 22, 39011, Santander, Spain
| | - Friedrich C Simmel
- Physik-Department E14 and ZNN/WSI, TU Munich, Am Coulombwall 4a, 85748, Garching, Germany.
| | - Fernando de la Cruz
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Consejo Superior de Investigaciones Científicas-SODERCAN, Albert Einstein 22, 39011, Santander, Spain.
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15
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O'Brien FG, Yui Eto K, Murphy RJT, Fairhurst HM, Coombs GW, Grubb WB, Ramsay JP. Origin-of-transfer sequences facilitate mobilisation of non-conjugative antimicrobial-resistance plasmids in Staphylococcus aureus. Nucleic Acids Res 2015; 43:7971-83. [PMID: 26243776 PMCID: PMC4652767 DOI: 10.1093/nar/gkv755] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 07/14/2015] [Indexed: 11/17/2022] Open
Abstract
Staphylococcus aureus is a common cause of hospital, community and livestock-associated infections and is increasingly resistant to multiple antimicrobials. A significant proportion of antimicrobial-resistance genes are plasmid-borne, but only a minority of S. aureus plasmids encode proteins required for conjugative transfer or Mob relaxase proteins required for mobilisation. The pWBG749 family of S. aureus conjugative plasmids can facilitate the horizontal transfer of diverse antimicrobial-resistance plasmids that lack Mob genes. Here we reveal that these mobilisable plasmids carry copies of the pWBG749 origin-of-transfer (oriT) sequence and that these oriT sequences facilitate mobilisation by pWBG749. Sequences resembling the pWBG749 oriT were identified on half of all sequenced S. aureus plasmids, including the most prevalent large antimicrobial-resistance/virulence-gene plasmids, pIB485, pMW2 and pUSA300HOUMR. oriT sequences formed five subfamilies with distinct inverted-repeat-2 (IR2) sequences. pWBG749-family plasmids encoding each IR2 were identified and pWBG749 mobilisation was found to be specific for plasmids carrying matching IR2 sequences. Specificity of mobilisation was conferred by a putative ribbon-helix-helix-protein gene smpO. Several plasmids carried 2–3 oriT variants and pWBG749-mediated recombination occurred between distinct oriT sites during mobilisation. These observations suggest this relaxase-in trans mechanism of mobilisation by pWBG749-family plasmids is a common mechanism of plasmid dissemination in S. aureus.
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Affiliation(s)
- Frances G O'Brien
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary Sciences and Life Sciences, Murdoch University and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia
| | - Karina Yui Eto
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia
| | - Riley J T Murphy
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia
| | - Heather M Fairhurst
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia
| | - Geoffrey W Coombs
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary Sciences and Life Sciences, Murdoch University and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia PathWest Laboratory Medicine, Fiona Stanley Hospital, Perth, Western Australia, Australia
| | - Warren B Grubb
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary Sciences and Life Sciences, Murdoch University and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia
| | - Joshua P Ramsay
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary Sciences and Life Sciences, Murdoch University and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia
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16
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Cabezón E, Ripoll-Rozada J, Peña A, de la Cruz F, Arechaga I. Towards an integrated model of bacterial conjugation. FEMS Microbiol Rev 2014; 39:81-95. [PMID: 25154632 DOI: 10.1111/1574-6976.12085] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Bacterial conjugation is one of the main mechanisms for horizontal gene transfer. It constitutes a key element in the dissemination of antibiotic resistance and virulence genes to human pathogenic bacteria. DNA transfer is mediated by a membrane-associated macromolecular machinery called Type IV secretion system (T4SS). T4SSs are involved not only in bacterial conjugation but also in the transport of virulence factors by pathogenic bacteria. Thus, the search for specific inhibitors of different T4SS components opens a novel approach to restrict plasmid dissemination. This review highlights recent biochemical and structural findings that shed new light on the molecular mechanisms of DNA and protein transport by T4SS. Based on these data, a model for pilus biogenesis and substrate transfer in conjugative systems is proposed. This model provides a renewed view of the mechanism that might help to envisage new strategies to curb the threating expansion of antibiotic resistance.
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Affiliation(s)
- Elena Cabezón
- Departamento de Biología Molecular, Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC, (Universidad de Cantabria, CSIC) Santander, Spain
| | - Jorge Ripoll-Rozada
- Departamento de Biología Molecular, Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC, (Universidad de Cantabria, CSIC) Santander, Spain
| | - Alejandro Peña
- Departamento de Biología Molecular, Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC, (Universidad de Cantabria, CSIC) Santander, Spain
| | - Fernando de la Cruz
- Departamento de Biología Molecular, Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC, (Universidad de Cantabria, CSIC) Santander, Spain
| | - Ignacio Arechaga
- Departamento de Biología Molecular, Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC, (Universidad de Cantabria, CSIC) Santander, Spain
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17
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Carballeira JD, González-Pérez B, Moncalián G, de la Cruz F. A high security double lock and key mechanism in HUH relaxases controls oriT-processing for plasmid conjugation. Nucleic Acids Res 2014; 42:10632-43. [PMID: 25123661 PMCID: PMC4176350 DOI: 10.1093/nar/gku741] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Relaxases act as DNA selection sieves in conjugative plasmid transfer. Most plasmid relaxases belong to the HUH endonuclease family. TrwC, the relaxase of plasmid R388, is the prototype of the HUH relaxase family, which also includes TraI of plasmid F. In this article we demonstrate that TrwC processes its target nic-site by means of a highly secure double lock and key mechanism. It is controlled both by TrwC–DNA intermolecular interactions and by intramolecular DNA interactions between several nic nucleotides. The sequence specificity map of the interaction between TrwC and DNA was determined by systematic mutagenesis using degenerate oligonucleotide libraries. The specificity map reveals the minimal nic sequence requirements for R388-based conjugation. Some nic-site sequence variants were still able to form the U-turn shape at the nic-site necessary for TrwC processing, as observed by X-ray crystallography. Moreover, purified TrwC relaxase effectively cleaved ssDNA as well as dsDNA substrates containing these mutant sequences. Since TrwC is able to catalyze DNA integration in a nic-site-containing DNA molecule, characterization of nic-site functionally active sequence variants should improve the search quality of potential target sequences for relaxase-mediated integration in any target genome.
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Affiliation(s)
- José Daniel Carballeira
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC, Universidad de Cantabria-CSIC, C/Albert Einstein 22, 39011 Santander, Spain
| | - Blanca González-Pérez
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC, Universidad de Cantabria-CSIC, C/Albert Einstein 22, 39011 Santander, Spain
| | - Gabriel Moncalián
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC, Universidad de Cantabria-CSIC, C/Albert Einstein 22, 39011 Santander, Spain
| | - Fernando de la Cruz
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC, Universidad de Cantabria-CSIC, C/Albert Einstein 22, 39011 Santander, Spain
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18
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Juhas M. Type IV secretion systems and genomic islands-mediated horizontal gene transfer in Pseudomonas and Haemophilus. Microbiol Res 2014; 170:10-7. [PMID: 25183653 DOI: 10.1016/j.micres.2014.06.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 06/28/2014] [Accepted: 06/30/2014] [Indexed: 11/16/2022]
Abstract
Bacterial secretion systems, such as type IV secretion systems (T4SSs) are multi-subunit machines transferring macromolecules across membranes. Besides proteins, T4SSs also transfer nucleoprotein complexes, thus having a significant impact on the evolution of bacterial species. By T4SS-mediated horizontal gene transfer bacteria can acquire a broad spectrum of fitness genes allowing them to thrive in the wide variety of environments. Furthermore, acquisition of antibiotic-resistance and virulence genes can lead to the emergence of novel 'superbugs'. This review provides an update on the investigation of T4SSs. It highlights the role T4SSs play in the horizontal gene transfer, particularly in the evolution of catabolic pathways, antibiotic-resistance and virulence in Haemophilus and Pseudomonas.
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Affiliation(s)
- Mario Juhas
- Department of Pathology, University of Cambridge, Tennis Court Road, CB2 1QP Cambridge, UK.
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19
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Lorenzo-Díaz F, Fernández-López C, Garcillán-Barcia MP, Espinosa M. Bringing them together: plasmid pMV158 rolling circle replication and conjugation under an evolutionary perspective. Plasmid 2014; 74:15-31. [PMID: 24942190 PMCID: PMC7103276 DOI: 10.1016/j.plasmid.2014.05.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 05/21/2014] [Accepted: 05/22/2014] [Indexed: 11/29/2022]
Abstract
The replication and transfer of rolling circle-replicating plasmids is reviewed. Comparisons of replication and transfer cassettes are presented. The current understanding of the pMV158 DNA transfer mechanism is reviewed.
Rolling circle-replicating plasmids constitute a vast family that is particularly abundant in, but not exclusive of, Gram-positive bacteria. These plasmids are constructed as cassettes that harbor genes involved in replication and its control, mobilization, resistance determinants and one or two origins of lagging strand synthesis. Any given plasmid may contain all, some, or just only the replication cassette. We discuss here the family of the promiscuous streptococcal plasmid pMV158, with emphasis on its mobilization functions: the product of the mobM gene, prototype of the MOBV relaxase family, and its cognate origin of transfer, oriT. Amongst the subfamily of MOBV1 plasmids, three groups of oriT sequences, represented by plasmids pMV158, pT181, and p1414 were identified. In the same subfamily, we found four types of single-strand origins, namely ssoA, ssoU, ssoW, and ssoT. We found that plasmids of the rolling-circle Rep_2 family (to which pMV158 belongs) are more frequently found in Lactobacillales than in any other bacterial order, whereas Rep_1 initiators seemed to prefer hosts included in the Bacillales order. In parallel, MOBV1 relaxases associated with Rep_2 initiators tended to cluster separately from those linked to Rep_1 plasmids. The updated inventory of MOBV1 plasmids still contains exclusively mobilizable elements, since no genes associated with conjugative transfer (other than the relaxase) were detected. These plasmids proved to have a great plasticity at using a wide variety of conjugative apparatuses. The promiscuous recognition of non-cognate oriT sequences and the role of replication origins for lagging-strand origin in the host range of these plasmids are also discussed.
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Affiliation(s)
- Fabián Lorenzo-Díaz
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria and Instituto Universitario de Enfermedades Tropicales y Salud Pública de Canarias, Centro de Investigaciones Biomédicas de Canarias, Universidad de La Laguna, Santa Cruz de Tenerife, Spain.
| | - Cris Fernández-López
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu, 9, E-28040 Madrid, Spain.
| | - M Pilar Garcillán-Barcia
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria - CSIC-SODERCAN, Santander, Cantabria, Spain.
| | - Manuel Espinosa
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu, 9, E-28040 Madrid, Spain.
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20
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Grove JI, Alandiyjany MN, Delahay RM. Site-specific relaxase activity of a VirD2-like protein encoded within the tfs4 genomic island of Helicobacter pylori. J Biol Chem 2013; 288:26385-96. [PMID: 23900838 PMCID: PMC3772185 DOI: 10.1074/jbc.m113.496430] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Four different type IV secretion systems are variously represented in the genomes of different Helicobacter pylori strains. Two of these, encoded by tfs3 and tfs4 gene clusters are contained within self-transmissible genomic islands. Although chromosomal excision of tfs4 circular intermediates is reported to be dependent upon the function of a tfs4-encoded XerD tyrosine-like recombinase, other factors required for transfer to a recipient cell have not been demonstrated. Here, we characterize the functional activity of a putative tfs4-encoded VirD2-like relaxase protein. Tfs4 VirD2 was purified as a fusion to maltose-binding protein and demonstrated to bind and nick both supercoiled duplex DNA and oligonucleotides in vitro in a manner dependent upon the presence of Mg(2+) but independently of any auxiliary proteins. Unusually, concentration-dependent nicking of duplex DNA appeared to require only transient protein-DNA interaction. Although phylogenetically distinct from established relaxase families, site-specific cleavage of oligonucleotides by Tfs4 VirD2 required the nick region sequence 5'-ATCCTG-3' common to transfer origins (oriT) recognized by MOBP conjugative relaxases. Cleavage resulted in covalent attachment of MBP-VirD2 to the 5'-cleaved end, consistent with conventional relaxase activity. Identification of an oriT-like sequence upstream of tfs4 virD2 and demonstration of VirD2 protein-protein interaction with a putative VirC1 relaxosome component indicate that transfer initiation of the tfs4 genomic island is analogous to mechanisms underlying mobilization of other integrated mobile elements, such as integrating conjugative elements, requiring site-specific targeting of relaxase activity to a cognate oriT sequence.
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Affiliation(s)
- Jane I Grove
- From the Centre for Biomolecular Sciences and Nottingham Digestive Diseases Centre, National Institute for Health Research Biomedical Research Unit, University of Nottingham, Nottingham NG7 2RD, United Kingdom
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21
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Abstract
HUH endonucleases are numerous and widespread in all three domains of life. The major function of these enzymes is processing a range of mobile genetic elements by catalysing cleavage and rejoining of single-stranded DNA using an active-site Tyr residue to make a transient 5'-phosphotyrosine bond with the DNA substrate. These enzymes have a key role in rolling-circle replication of plasmids and bacteriophages, in plasmid transfer, in the replication of several eukaryotic viruses and in various types of transposition. They have also been appropriated for cellular processes such as intron homing and the processing of bacterial repeated extragenic palindromes. Here, we provide an overview of these fascinating enzymes and their functions, using well-characterized examples of Rep proteins, relaxases and transposases, and we explore the molecular mechanisms used in their diverse activities.
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22
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Messing SAJ, Ton-Hoang B, Hickman AB, McCubbin AJ, Peaslee GF, Ghirlando R, Chandler M, Dyda F. The processing of repetitive extragenic palindromes: the structure of a repetitive extragenic palindrome bound to its associated nuclease. Nucleic Acids Res 2012; 40:9964-79. [PMID: 22885300 PMCID: PMC3479197 DOI: 10.1093/nar/gks741] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Extragenic sequences in genomes, such as microRNA and CRISPR, are vital players in the cell. Repetitive extragenic palindromic sequences (REPs) are a class of extragenic sequences, which form nucleotide stem-loop structures. REPs are found in many bacterial species at a high copy number and are important in regulation of certain bacterial functions, such as Integration Host Factor recruitment and mRNA turnover. Although a new clade of putative transposases (RAYTs or TnpAREP) is often associated with an increase in these repeats, it is not clear how these proteins might have directed amplification of REPs. We report here the structure to 2.6 Å of TnpAREP from Escherichia coli MG1655 bound to a REP. Sequence analysis showed that TnpAREP is highly related to the IS200/IS605 family, but in contrast to IS200/IS605 transposases, TnpAREP is a monomer, is auto-inhibited and is active only in manganese. These features suggest that, relative to IS200/IS605 transposases, it has evolved a different mechanism for the movement of discrete segments of DNA and has been severely down-regulated, perhaps to prevent REPs from sweeping through genomes.
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Affiliation(s)
- Simon A J Messing
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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Agúndez L, González-Prieto C, Machón C, Llosa M. Site-specific integration of foreign DNA into minimal bacterial and human target sequences mediated by a conjugative relaxase. PLoS One 2012; 7:e31047. [PMID: 22292089 PMCID: PMC3264647 DOI: 10.1371/journal.pone.0031047] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 12/30/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Bacterial conjugation is a mechanism for horizontal DNA transfer between bacteria which requires cell to cell contact, usually mediated by self-transmissible plasmids. A protein known as relaxase is responsible for the processing of DNA during bacterial conjugation. TrwC, the relaxase of conjugative plasmid R388, is also able to catalyze site-specific integration of the transferred DNA into a copy of its target, the origin of transfer (oriT), present in a recipient plasmid. This reaction confers TrwC a high biotechnological potential as a tool for genomic engineering. METHODOLOGY/PRINCIPAL FINDINGS We have characterized this reaction by conjugal mobilization of a suicide plasmid to a recipient cell with an oriT-containing plasmid, selecting for the cointegrates. Proteins TrwA and IHF enhanced integration frequency. TrwC could also catalyze integration when it is expressed from the recipient cell. Both Y18 and Y26 catalytic tyrosil residues were essential to perform the reaction, while TrwC DNA helicase activity was dispensable. The target DNA could be reduced to 17 bp encompassing TrwC nicking and binding sites. Two human genomic sequences resembling the 17 bp segment were accepted as targets for TrwC-mediated site-specific integration. TrwC could also integrate the incoming DNA molecule into an oriT copy present in the recipient chromosome. CONCLUSIONS/SIGNIFICANCE The results support a model for TrwC-mediated site-specific integration. This reaction may allow R388 to integrate into the genome of non-permissive hosts upon conjugative transfer. Also, the ability to act on target sequences present in the human genome underscores the biotechnological potential of conjugative relaxase TrwC as a site-specific integrase for genomic modification of human cells.
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MESH Headings
- Base Sequence
- Chromosomes, Bacterial/genetics
- Chromosomes, Bacterial/metabolism
- Chromosomes, Human/genetics
- Chromosomes, Human/metabolism
- Cloning, Molecular/methods
- Conjugation, Genetic/genetics
- Conjugation, Genetic/physiology
- DNA/genetics
- DNA/metabolism
- DNA Nucleotidyltransferases/metabolism
- DNA Nucleotidyltransferases/physiology
- DNA, Bacterial/genetics
- DNA, Bacterial/metabolism
- Escherichia coli Proteins/metabolism
- Escherichia coli Proteins/physiology
- Gene Targeting/methods
- Humans
- Integrases/genetics
- Integrases/metabolism
- Models, Biological
- Mutagenesis, Insertional/physiology
- Mutagenesis, Site-Directed/methods
- Organisms, Genetically Modified
- Plasmids/genetics
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Affiliation(s)
- Leticia Agúndez
- Departamento de Biología Molecular, Universidad de Cantabria (UC) and Instituto de Biomedicina y Biotecnología de Cantabria, UC-CSIC-SODERCAN, Santander, Spain
| | - Coral González-Prieto
- Departamento de Biología Molecular, Universidad de Cantabria (UC) and Instituto de Biomedicina y Biotecnología de Cantabria, UC-CSIC-SODERCAN, Santander, Spain
| | - Cristina Machón
- Departamento de Biología Molecular, Universidad de Cantabria (UC) and Instituto de Biomedicina y Biotecnología de Cantabria, UC-CSIC-SODERCAN, Santander, Spain
| | - Matxalen Llosa
- Departamento de Biología Molecular, Universidad de Cantabria (UC) and Instituto de Biomedicina y Biotecnología de Cantabria, UC-CSIC-SODERCAN, Santander, Spain
- * E-mail:
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24
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Lorenzo-Díaz F, Dostál L, Coll M, Schildbach JF, Menéndez M, Espinosa M. The MobM relaxase domain of plasmid pMV158: thermal stability and activity upon Mn2+ and specific DNA binding. Nucleic Acids Res 2011; 39:4315-29. [PMID: 21296755 PMCID: PMC3105389 DOI: 10.1093/nar/gkr049] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Protein MobM, the relaxase involved in conjugative transfer of the streptococcal plasmid pMV158, is the prototype of the MOBV superfamily of relaxases. To characterize the DNA-binding and nicking domain of MobM, a truncated version of the protein (MobMN199) encompassing its N-terminal region was designed and the protein was purified. MobMN199 was monomeric in contrast to the dimeric form of the full-length protein, but it kept its nicking activity on pMV158 DNA. The optimal relaxase activity was dependent on Mn2+ or Mg2+ cations in a dosage-dependent manner. However, whereas Mn2+ strongly stabilized MobMN199 against thermal denaturation, no protective effect was observed for Mg2+. Furthermore, MobMN199 exhibited a high affinity binding for Mn2+ but not for Mg2+. We also examined the binding-specificity and affinity of MobMN199 for several substrates of single-stranded DNA encompassing the pMV158 origin of transfer (oriT). The minimal oriT was delimited to a stretch of 26 nt which included an inverted repeat located eight bases upstream of the nick site. The structure of MobMN199 was strongly stabilized by binding to the defined target DNA, indicating the formation of a tight protein–DNA complex. We demonstrate that the oriT recognition by MobMN199 was highly specific and suggest that this protein most probably employs Mn2+ during pMV158 transfer.
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Affiliation(s)
- Fabián Lorenzo-Díaz
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain
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25
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Dostál L, Shao S, Schildbach JF. Tracking F plasmid TraI relaxase processing reactions provides insight into F plasmid transfer. Nucleic Acids Res 2010; 39:2658-70. [PMID: 21109533 PMCID: PMC3074121 DOI: 10.1093/nar/gkq1137] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Early in F plasmid conjugative transfer, the F relaxase, TraI, cleaves one plasmid strand at a site within the origin of transfer called nic. The reaction covalently links TraI Tyr16 to the 5′-ssDNA phosphate. Ultimately, TraI reverses the cleavage reaction to circularize the plasmid strand. The joining reaction requires a ssDNA 3′-hydroxyl; a second cleavage reaction at nic, regenerated by extension from the plasmid cleavage site, may generate this hydroxyl. Here we confirm that TraI is transported to the recipient during transfer. We track the secondary cleavage reaction and provide evidence it occurs in the donor and F ssDNA is transferred to the recipient with a free 3′-hydroxyl. Phe substitutions for four Tyr within the TraI active site implicate only Tyr16 in the two cleavage reactions required for transfer. Therefore, two TraI molecules are required for F plasmid transfer. Analysis of TraI translocation on various linear and circular ssDNA substrates supports the assertion that TraI slowly dissociates from the 3′-end of cleaved F plasmid, likely a characteristic essential for plasmid re-circularization.
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Affiliation(s)
- Lubomír Dostál
- Department of Biology, Johns Hopkins University, 3400 N. Charles St, Baltimore, MD 21218, USA
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26
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Nuclear targeting of a bacterial integrase that mediates site-specific recombination between bacterial and human target sequences. Appl Environ Microbiol 2010; 77:201-10. [PMID: 21037296 DOI: 10.1128/aem.01371-10] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
TrwC is a bacterial protein involved in conjugative transfer of plasmid R388. It is transferred together with the DNA strand into the recipient bacterial cell, where it can integrate the conjugatively transferred DNA strand into its target sequence present in the recipient cell. Considering that bacterial conjugation can occur between bacteria and eukaryotic cells, this protein has great biotechnological potential as a site-specific integrase. We have searched for possible TrwC target sequences in the human genome. Recombination assays showed that TrwC efficiently catalyzes recombination between its natural target sequence and a discrete number of sequences, located in noncoding sites of the human genome, which resemble this target. We have determined the cellular localization of TrwC and derivatives in human cells by immunofluorescence and also by an indirect yeast-based assay to detect both nuclear import and export signals. The results indicate that the recombinase domain of TrwC (N600) has nuclear localization, but full-length TrwC locates in the cytoplasm, apparently due to the presence of a nuclear export signal in its C-terminal domain. The recombinase domain of TrwC can be transported to recipient cells by conjugation in the presence of the helicase domain of TrwC, but with very low efficiency. We mutagenized the trwC gene and selected for mutants with nuclear localization. We obtained one such mutant with a point A904T mutation and an extra peptide at its C terminus, which maintained its functionality in conjugation and recombination. This TrwC mutant could be useful for future TrwC-mediated site-specific integration assays in mammalian cells.
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27
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ICEEc2, a new integrative and conjugative element belonging to the pKLC102/PAGI-2 family, identified in Escherichia coli strain BEN374. J Bacteriol 2010; 192:5026-36. [PMID: 20675467 DOI: 10.1128/jb.00609-10] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The diversity of the Escherichia coli species is in part due to the large number of mobile genetic elements that are exchanged between strains. We report here the identification of a new integrative and conjugative element (ICE) of the pKLC102/PAGI-2 family located downstream of the tRNA gene pheU in the E. coli strain BEN374. Indeed, this new region, which we called ICEEc2, can be transferred by conjugation from strain BEN374 to the E. coli strain C600. We were also able to transfer this region into a Salmonella enterica serovar Typhimurium strain and into a Yersinia pseudotuberculosis strain. This transfer was then followed by the integration of ICEEc2 into the host chromosome downstream of a phe tRNA gene. Our data indicated that this transfer involved a set of three genes encoding DNA mobility enzymes and a type IV pilus encoded by genes present on ICEEc2. Given the wide distribution of members of this family, these mobile genetic elements are likely to play an important role in the diversification of bacteria.
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Nash RP, Habibi S, Cheng Y, Lujan SA, Redinbo MR. The mechanism and control of DNA transfer by the conjugative relaxase of resistance plasmid pCU1. Nucleic Acids Res 2010; 38:5929-43. [PMID: 20448025 PMCID: PMC2943615 DOI: 10.1093/nar/gkq303] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Bacteria expand their genetic diversity, spread antibiotic resistance genes, and obtain virulence factors through the highly coordinated process of conjugative plasmid transfer (CPT). A plasmid-encoded relaxase enzyme initiates and terminates CPT by nicking and religating the transferred plasmid in a sequence-specific manner. We solved the 2.3 Å crystal structure of the relaxase responsible for the spread of the resistance plasmid pCU1 and determined its DNA binding and nicking capabilities. The overall fold of the pCU1 relaxase is similar to that of the F plasmid and plasmid R388 relaxases. However, in the pCU1 structure, the conserved tyrosine residues (Y18,19,26,27) that are required for DNA nicking and religation were displaced up to 14 Å out of the relaxase active site, revealing a high degree of mobility in this region of the enzyme. In spite of this flexibility, the tyrosines still cleaved the nic site of the plasmid’s origin of transfer, and did so in a sequence-specific, metal-dependent manner. Unexpectedly, the pCU1 relaxase lacked the sequence-specific DNA binding previously reported for the homologous F and R388 relaxase enzymes, despite its high sequence and structural similarity with both proteins. In summary, our work outlines novel structural and functional aspects of the relaxase-mediated conjugative transfer of plasmid pCU1.
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Affiliation(s)
- Rebekah Potts Nash
- Department of Chemistry, University of North Carolina, Chapel Hill, CB 3290 and Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, CB 7260, Chapel Hill, NC 27599, USA
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